The present invention relates to a method for applying a structure, in particular a marking or inscription, to at least one element by meats of a marking, system, and to a method for producing an angle measurement system or a component of an angle measurement system, and to an angle measurement system or component of an angle measurement system produced by means of this method.
It is particularly the case in angle measurement systems that the scales used for determining the angle must be applied with a high degree of precision. A inscription method is known from the prior art, in particular from DE 100 19 499, in which a signal carrier is attached in an inscription device having a rotational axis and the signal carrier is rotated about the rotational axis. An eccentricity of the centre of the signal carrier relative to the rotational axis is detected and the corrected value is taken into account when applying the marking.
It is likewise known from the prior art, e.g. DE 10 2005 021 504 to adjust the body, to be provided with a marking, on a support device of the inscription system, wherein the adjustment takes place via the mutual alignment of markings on the body and the support device.
However, a disadvantage of the known methods is that although the eccentricity of the signal carrier or of the element to be provided with the inscription relative to the reference axis of the inscription system is taken into account, the element is mounted on the angle measurement system after inscription, which system can likewise have manufacturing tolerances or unbalances. This leads, in turn, to an inaccuracy during distance or angle measurement since the manufacturing tolerances or even the dynamic imbalance of the bearing of the angle measurement system itself have not been taken into account.
In order to counteract these problems, the angle measurement systems themselves must be manufactured with an extremely high degree of precision, which is very expensive and complex.
It is desirable to provide a simplified method for producing a structure on an element, in particular on an element for an angle measurement system which allows precise measurements.
A method for producing a structure, a method for producing an angle measurement system or component of an angle measurement, and an angle measurement system or a component of an angle measurement system are provided.
The term “component” is understood to mean a single-piece or multi-piece component.
In accordance with the invention, a method for applying a structure, in particular a marking and/or inscription, to at least one element with a marking system, in particular a laser system is provided, wherein the at least one element is arranged relative to a shaft. The invention is based on the idea of arranging, in a first step a), the shaft, onto which the element will subsequently be arranged or attached, and/or the shaft together with the element arranged relative to the shaft, in the marking system. In a second step b), a spatial position and/or a centre of rotation of the shaft in relation to a reference point, preferably an origin, of the marking system is/are determined and then in step c) a structure is applied to the element arranged relative to the shaft. As a result, it is not the eccentricity of the element itself which is determined, as in the prior art, but the spatial position of the shaft, preferably its centre of rotation, relative to which the element is to be arranged, and therefore manufacturing inaccuracies are reduced and dynamic imbalances of the shaft bearing are also taken into account. Additionally, since the element is already at its assembly position whilst the structure is applied, the production of the angle measurement system can thus be significantly simplified.
In accordance to a further advantageous embodiment of the inventive method, the structure is applied taking into account the determination of the spatial position and/or the centre of rotation of the shaft. This means that, in contrast to the prior art, in which an eccentricity of the element is decisive for the correction values when applying the structure, this eccentricity of the element is not taken into account at all in the inventive method when applying the structure and only the spatial position or centre of rotation of the shaft is of interest. This is particularly possible since the element does not have to be arranged on another shaft, but remains on the measured shaft.
In accordance to a further advantageous embodiment, the shaft and/or the shaft with the element arranged relative to the shaft remains in the marking system during all steps following step a). In an advantageous manner, the precision can be further increased since imperfection sources due to dismounting the shaft from the marking system are avoided. At the same time, the method can be simplified since the spatial position of the shaft does not have to be measured again.
In accordance to a further advantageous embodiment, a measuring body is used, in particular for determining the relation of the spatial position and/or centre of rotation of the shaft to a reference point of the marking system, wherein the measuring body is preferably placed on the shaft in a form-fitting manner. By means of this inventive measuring body, the spatial position or centre of rotation of the shaft relative to a reference point of the marking system can be uniquely determined. Thereby, the measuring body can be formed as an active and/or passive measuring body. Exemplarily, a sensor providing signals may be considered, as an active measuring body, wherein the signals may be used to (actively) determine the spatial position of the shaft, and wherein the active measuring body transmits the measured signals, for example, to the marking system directly and/or even to a control system which in turn is connected to the marking system.
Alternatively or additionally, a passive measuring body can also be used which is preferably pre-measured by means of the marking system, whereby in turn the spatial position or centre of rotation of the shaft can be determined. To this end, a marking can be applied onto the measuring body for example, which marking is detected by means of the marking system. Depending upon where the marking is located, the marking system may then determine the spatial position or centre of rotation of the shaft. Such a marking can be previously applied to the measuring body but it is also possible to apply, and then measure, this marking by means of the marking system.
However, at the same time it is also possible to determine the spatial position or centre of rotation of the shaft merely from the geometric shape of the measuring body.
The measuring body itself, in whatever design, advantageously permits a simple and rapid determination of the spatial position or centre of rotation of the shaft, and therefore the method is in turn simplified.
If a measuring marking, is applied on the measuring body, then it is particularly advantageous if the marking system, which preferably comprises at least one suitable radiation source for determining the spatial position and/or centre of rotation of the shaft, irradiates the measuring marking, wherein preferably the measuring marking is formed such that, upon irradiation with the radiation source the measuring marking shows a different reflection behaviour at the at least one structured location than at an unstructured location. Since a radiation source is typically already provided on a marking system, a measuring marking formed in this manner can be used to determine the spatial position or centre of rotation of the shaft in a particularly simple manner.
In accordance to a further advantageous embodiment, the measuring body is removed from the shaft, prior to applying the structure. Thereby, it can be ensured that the shaft remains in the marking system whilst only the measuring body is removed.
A further advantageous step of the inventive method comprises the rotation of the shaft for determining the spatial position and/or centre of rotation of the shaft. The spatial position of the shaft itself or the centre of rotation thereof can be measured before and/or after and/or even during this rotation, or a measuring body placed on the shaft can, as described above, assist to uniquely determine the spatial position of the shaft or the centre of rotation thereof. Of course, instead of the shaft, the device can also be rotated about the shaft, wherein in this case preferably the measuring body is placed on the device.
In accordance with a further advantageous embodiment, a lower energy density of the marking system is applied for the step of determining the centre of rotation and/or the spatial position of the shall than for the step of applying the structure. It is particularly preferred if the marking system is formed as a laser system. As already described above, the marking system can also be designed to scan a measuring marking applied to a measuring body. However, in order to do this without causing damage, it is advantageous to set the energy density of the marking system such that no structural damage or effects occur on the measuring body. It is particularly preferred if the energy density is below the marking threshold of the material used. This means, for example, that when using a laser, the laser can be actuated or used at a first energy density which has no effect on the material of the measuring body and/or on the element provided with a structure, and which is merely used to determine the spatial position or centre of rotation of the shaft. In contrast to that, a second energy density is adapted so that a structure can be applied to the element. Such a structure is mostly permanent, since in the region of the structure the material properties of the element are changed due to the energy density applied by the radiation source, in particular by the laser.
In accordance with a further advantageous embodiment, the inventive method comprises the step of attaching the element to the shaft or to a device including the shaft, wherein the step of attaching the element occurs before step a). i.e. the step of arranging the shaft in the marking system, or before step c), namely applying the structure. Again, the shaft preferably remains in the marking, system, and therefore an imperfection is not implemented due to the dismounting of the shaft from the marking system. Alternatively, in order to attach the element to the shaft, the shaft may once more be removed from the marking system.
It can be further advantageous to once again perform the step of determining the spatial position. Since the structure is only applied to the element when the element is attached to the shaft or is arranged relative to the shaft, it is irrelevant whether the eccentricity of the element has been determined. The decisive factor for avoiding imperfections in the inventive method is the measuring of the spatial position of the shaft, to/on which the element is attached or arranged.
In accordance with a further advantageous embodiment, the inventive method may be used not only to provide a single element with a structure but also to provide a plurality of elements, to be arranged relative to the shaft, with a structure by means of the method. Thereby, for any further element, only the attaching step and the step of applying the structure are performed. As a result, the method can again be simplified and accelerated.
Preferably, only after having applied all the structures to all the elements to be arranged relative to the shaft, the shaft, together with the elements arranged thereon, is removed from the marking system. As a result, the spatial position of the shaft only has to be measured only once, whereby the marking method can be performed considerably more quickly and more precisely. In addition, the inventive method may be used to produce highly-precise structures on mutually rotatable elements which are aligned precisely with one another, since no further imperfections may occur due to only subsequently mounting the finished structured elements on a shaft. In addition, after applying the last structure to the last element, a finished structured element, in particular a finished mounted component for an angle measurement system, may be removed from the marking system preferably together with the device in which it was installed.
As already indicated above, it is particularly preferred to use the method to produce an angle measurement system or a component for an angle measurement system. Therefore, a further aspect of the present invention relates to a method for producing an angle measurement system or a component thereof, wherein the angle measurement system or the component comprises at least one element having a preferably optically effective structure, wherein the structure is applied to the element in accordance with the above-described method.
Angle measurement systems are available in a wide variety of designs and typically include a first element having a first structure and a second element which can be rotated with respect to the first element and has a second structure. Furthermore, at least one radiation source may be provided which emits radiation to the first element with the preferably optically effective structure, formed as a measuring structure, and along the radiation path to an optically effective reference structure, i.e. a second element. Diffraction grating structures may frequently be used as the optically effective structures. Since the radiation of the radiation source is modulated via the optically effective structure of the measuring structure and the optically effective structure of the reference structure depending upon the spatial position of the structures with respect to each other, this modulation can be used to determine the relative position of the two optical structures with respect to each other. However, thereby, the optically effective structures of the measuring structure and of the reference element have to be precisely aligned with respect to each other. At the same time, the optically effective structures have to be be formed extremely finely in order to be able to provide a sufficiently high resolution. Imprecise alignment of the structures with respect to each other, which can occur for example due to manufacturing inaccuracies and dynamic imbalances of the shaft bearing, can lead to angle errors or to an angle-dependent amplitude of the measuring signal and, on the basis thereof, to the problem of the measuring signal possibly disappearing.
The inventive method for applying a structure to an element may be used to solve this problem since the structure is applied to the element arranged relative to the shaft not relative to a positioned element but relative to the positioned shaft, preferably to the positioned centre of rotation of the shaft. As a result, imperfections which occur from a lack of adjustment or simply imprecise adjustment of the elements on the shaft or a dynamic imbalance, can advantageously be avoided. At the same time, the method for producing, an angle measurement system or a component of an angle measurement system can be simplified as a result since subsequent time- and cost-intensive affixing of the separately structured element to the shaft of the angle measurement system is not necessary.
In accordance with a further advantageous embodiment, the angle measurement system or the component of the angle measurement system comprises a structural unit having a rotatable shaft on which at least one first and one second element can be arranged which are formed to be rotatable with respect to each other, wherein the first element is arranged for co-rotation with the unit and the second element is arranged for co-rotation with the shaft to which the structure is applied in the arranged state.
It is particularly preferred if the following steps are performed:    1. attaching the first element to the structural unit for co-rotation therewith and arranging the structural unit in the marking system;    2. affixing a measuring body to the shaft of the structural unit;    3. rotating the shaft and determining a centre of rotation and/or a spatial position of the shaft in relation to a reference point, in particular an origin of the marking system by means of the marking system using the measuring body;    4. removing the measuring body;    5. applying the optically effective structure to the first element;    6. attaching the second element to the shaft for co-rotation therewith;    7. applying the optically effective structure to the second element;    8. removing the structural unit from the marking system.
During steps 2 to 7, the structural unit remains in the marking system. As a result, it can be ensured that the optically effective structures of the first or second element are optimally aligned with respect to each other, and therefore a virtually distortion-free angle determination is permitted or the signal cannot disappear due to dynamic imbalances or mounting imperfections.
Preferably, steps 6 and 7 of the inventive are performed until all the elements to be attached to the structural unit are provided with an optically effective structure.
In accordance with a further advantageous embodiment, the structural unit of the angle measurement system may be connected to a drive unit with a rotatable shaft or is formed as a drive unit with a rotatable shaft, wherein the first element is arranged for co-rotation with the structural unit or the drive unit and the second element is arranged for co-rotation with the shaft. It is particularly advantageous that the angle measurement system can already be fitted with the drive unit during production thereof, whereby additional mounting steps which are encumbered with imperfections can be omitted due to the arrangement of the angle measurement system on a shaft of a drive unit.
A further aspect of the present invention relates to an angle measurement system or a component of an angle measurement system which is produced as described above or which comprises an element with a structure, wherein the structure is applied to the element as described above.
Further advantages and advantageous embodiments are defined in the claims, the description and the drawings.
Like elements and elements acting in a functionally identical manner are designated with the same reference signs hereinafter.